The present invention relates to a kind of distance meter, and more specifically relates to a distance meter telescope.
Distance meter is a kind of equipment that makes use of the reflection and interference of lights, sounds and electromagnetic waves to measure lengths and distances. On the basis of measuring lengths, some newly developed distance meters can also perform scientific calculations of different parameters such as surface areas, perimeters, sizes and masses of the target objects based on the measured lengths. Distances meters have a wide range of applications in various fields such as engineering, GIS investigations and military affairs.
Distance meter telescope is a branch of laser distance meter. Distance meter telescope may be called a long distance laser distance meter, which generally uses pulse ranging method to measure distance. Said pulse ranging method is that, laser emitted from a distance meter is reflected by the target object and again received by the distance meter, and the distance meter simultaneously records the laser travelling time to and from the target object. The distance between the distance meter and the target object is half of the product of the speed of laser times the total laser travelling time to and from the target object. Distance measurement by pulse ranging method has a general accuracy of around +/− one meter.
FIG. 1 shows a kind of known optical distance measurement device. Such optical distance measurement device has been disclosed in Chinese granted patent publication number CN100403090C. The optical distance measurement device 90 according to this patent comprises an optical emission system 92 and an observation/receiving optical system 91. The observation/receiving optical system 91 comprises a first lens 94, a light splitting and merging prisms group 20, a display module 95, a detector 99 and an eyepiece 97. The optical emission system 92 comprises a second lens 98 and an emission assembly 96. Light rays which are within the visible light spectrum representing an image of the target object emit towards the optical distance measurement device from the first lens 94; next, the visible light rays emit to the light splitting and merging prisms group 20 via a first light input/output surface 213. In the light splitting and merging prisms group 20, the light rays travel along a path of a first wavelength beam r1 and leave from the second light input/output surface 223; after that, the light rays pass through the eyepiece 97 so that an observer can clearly see the target object. The emission assembly 96 comprises a laser diode 961 and a lens group 962, and emits infrared light rays. The infrared light rays pass through the second lens 98 and travel to the target object. The target object reflects the infrared light rays. Some of the reflected infrared light rays emit to the observation/receiving optical system 91 through the first lens 94. In the observation/receiving optical system 91, the infrared light rays pass through the first light input/output surface 213 of a roof prism 21 and travel to the light splitting and merging prisms group 20; then the infrared light rays travel along a path of a second wavelength beam r2, and leave from a fourth input/output surface 232 of a compensation prism; lastly, the detector 99 receives the infrared light rays. Accordingly, the optical distance measuring device 90 calculates a distance between the optical distance measuring device and the target object based on the travelling time of the infrared light rays to and from the target object and the optical distance measuring device. The display module 95 such as an LCD component or LED digital display unit emits light rays of predefined narrow wavelengths to display the measured distance. The light rays of predefined wavelengths emitted by the display module 95 comes from the second input/output surface 231 of the compensation prism 23, and emit into the light splitting and merging prisms group 20. The light rays of narrow wavelengths travel along the path of the second wavelength beam r2, and leave from the second light input/output surface 223. Consequently, the light rays of narrow wavelengths travel through the eyepiece 97 so that the observer can clearly see the numbers displayed by the display module.
In short, the according the prior art, the compensation prism 23 of an optical distance measuring device is a pentaprism which has a complicated structure and a high manufacture cost. Also, due to structural issue, clear apertures of the infrared light rays and the light rays emitted from the display module 95 will be limited.